含钒石煤提钒的试验研究

以含钒石煤原矿及浮选精矿为原料,分别进行了原矿、选矿精矿直接酸浸及活化-浸出工艺的研究。研究结果表明：精矿在酸矿比0.6、200℃活化-浸出条件下,钒的浸出率为90.69%,酸耗约35 t酸/t V2O5;精矿活化-浸出工艺具有处理量小、无需加入添加剂、酸耗低等经济、技术上的优势。     

我国企业协会的覆盖率及其相关制度的再设计

企业协会要行使行业代表、行业管理职能必须具有高的行业覆盖率。由于形成的途经的不同和产业链的细分，我国许多行业中普遍存在着“一业多会”现象，导致了企业协会的覆盖率降低、内耗严重，协会的应有功能无法充分发挥。研究表明：走出“一业多会”困境的出路在于强制入会制度的实施、政府背景的隐退和业务主管部门的取消，以及政府行业管理职能的择优转移和“第三部门”的形成。     

Is the protection of beach and dune vegetation compatible with tourism?

The paradox of development vs. protection and conservation of the coasts highlights the need to determine if tourism and conservation can be compatible rather than opposite activities. We analyzed the spatial and temporal changes in vegetation cover, composition and diversity in three beaches located in the state of Veracruz (Mexico) with different levels of tourism activity (Natural, Trailer Park and Hotels). We calculated tourist density and evaluated vegetation cover, species richness and diversity and analyzed the changes before and after three holiday seasons (winter, spring and summer). The Natural site had the highest vegetation cover (42.8 m²), species richness (14) and diversity (1.50), and Trailer Park the lowest (4.9 m², 8 species, and 0.897 respectively). The BACI (Before-After-Control-Design) analysis showed no significant differences before and after the holiday seasons. Our results show how low and medium density tourism can be compatible with the protection of beach and coastal dune vegetation.     

我国矿产资源开发利用现状与发展策略

矿产资源是人类赖以生存发展的物质基础,在现代化建设中占有重要的地位。我国是世界上矿产资源比较丰富、矿种比较齐全的少数几个国家之一。具有资源总量丰富但人均占有量少;矿床规模有大有小;贫矿多且富矿少等特点。多年来由于矿产资源的不合理开发利用,造成严重的环境污染。在我国许多地区废矿石大量堆放,地表水和地下水严重污染,区域地下水位下降,土壤和空气也受到侵害。为保证２１世纪我国国民经济的持续发展,必须采取以下几个方面的对策：①加强和改善矿产资源的管理;②加强地质勘查工作,增加矿产资源探明储量以适应国民经济的发展;③实行开源与节流并重的方针,走资源节约型发展经济的道路;④充分认识我国矿产资源的产出特点,完善矿产开发的产业机制;⑤依靠法制和科学管理,有效控制环境污染,保护矿产资源。     

论中国金刚石原生矿的找矿前景(下)

⑵ 华北地台的演化发展及构造格局 　　华北地台属于太古代克拉通。其结晶基底和褶皱基底分别由太古代陆核和元古代古褶皱带构成。太古代末期的阜平运动 (2600Ma)使华北及其邻近地区经历了普遍而强烈的构造运动和变形—变质作用,形成古陆核,奠定了华北地台的基础。元古代中     

Financial density selection

We propose and study simple but flexible methods for density selection of skewed versions of the two most popular density classes in finance, the exponential power distribution and the t distribution. For the first type of method, which simply consists of selecting a density by means of an information criterion, the Schwarz criterion stands out since it performs well across density categories, and in particular when the DGP is normal. For the second type of method, general-to-specific density selection, the simulations suggest that it can improve the recovery rate in predictable ways by changing the significance level. This is useful because it enables us to increase (reduce) the recovery rate of non-normal densities by increasing (reducing) the significance level, if one wishes to do so. The third type of method is a generalisation of the second type, such that it can be applied across an arbitrary number of density classes, nested or non-nested. Finally, the methods are illustrated in an empirical application.     

The shape of small sample biases in pricing kernel estimations

Numerous empirical studies find pricing kernels that are not-monotonically decreasing; the findings are at odds with the pricing kernel being marginal utility of a risk-averse, so-called representative agent. We study in detail the common procedure which estimates the pricing kernel as the ratio of two separate density estimations. In the first step, we analyse theoretically the functional dependence for the ratio of a density to its estimated density; this cautions the reader regarding potential computational issues coupled with statistical techniques. In the second step, we study this quantitatively; we show that small sample biases shape the estimated pricing kernel, and that estimated pricing kernels typically violate the commonly believed monotonicity at the centre even when the true pricing kernel fulfils these. This contributes to an alternative, statistical explanation for the puzzling shape in pricing kernel estimations.     

Analysing Tax–Benefit Reforms Using Non‐Parametric Methods*

Static tax–benefit microsimulation models (MSMs) are widely used and well‐regarded tools for public policy analysis, but it is essential to use them very carefully. This paper focuses on the analysis of MSM output, suggesting the use of non‐parametric methods as a useful, informative and relatively straightforward complement to detect effects not always captured by measures often used to present MSM results. Non‐parametric methods are used here to analyse the output of an MSM applied to the 1998 Italian personal income tax reform, the main change in which concerned the tax schedule: the first tax rate was increased from 10 per cent to 18.5 per cent and the top one was reduced by 4.5 percentage points. Non‐parametric methods highlight that the effects of this reform were very different for different types of households, with low‐income pensioner households among the main losers. Results are checked for robustness by standard statistical methods and compared with empirical results obtainable using quintile histograms.     

县域经济发展的空间集聚特征与优化思路--以重庆市为例

地区之间人口集聚程度和经济集聚程度的差异是现实世界中普遍存在的特征和事实,这个变化趋势在全球范围内迄今依然是有增无减,而且集聚的大潮将不可阻挡。因此本文以经济密度和集聚程度作为主要指标,对重庆市2010年38个区县的集聚发展状况进行了分析,分析结果表明各区县的集聚发展并不平衡,具体可以划分为4个不同的集聚发展类型。从空间格局上看,主要呈现出如下特征：（1）“两翼”区县集聚发展程度整体偏低,（2）“一圈”内部存在差异,（3）长江南北存在明显差距。最后,结合前述分析结论和不同区县所属主体功能区类型,本文提出了有针对性的差异化集聚发展思路,以便促进全市区域经济更加科学协调发展。     

A logistic regression point of view toward loss given default distribution estimation

We propose a new procedure to estimate the loss given default (LGD) distribution. Owing to the complicated shape of the LGD distribution, using a smooth density function as a driver to estimate it may result in a decline in model fit. To overcome this problem, we first apply the logistic regression to estimate the LGD cumulative distribution function. Then, we convert the result into the LGD distribution estimate. To implement the newly proposed estimation procedure, we collect a sample of 5269 defaulted debts from Moody’s Default and Recovery Database. A performance study is performed using 2000 pairs of in-sample and out-of-sample data-sets with different sizes that are randomly selected from the entire sample. Our results show that the newly proposed procedure has better and more robust performance than its alternatives, in the sense of yielding more accurate in-sample and out-of-sample LGD distribution estimates. Thus, it is useful for studying the LGD distribution.